In numerous instances, and particularly in completion of underwater oil and gas wells, it is necessary to connect a load to an upper member from which the load is to be suspended, with the weight of the load being large, the space available to accomplish the coupling being transversely small, and with the requirement that operation of the coupling be accomplished remotely. One example of such a requirement arises in the suspension of tubing strings in an underwater well, the tubing strings depending from a tubing hanger which must be landed in a wellhead structure, on the floor of the body of water, by a handling string connected to the tubing hanger by a handling tool, the handling string being manipulated from a vessel or other operational base at the surface of the body of water. Weight of the tubing strings is as much as 300,000 pounds or more. The wellhead or like structure may be in deep water, frequently beyond the depths at which a diver can operate, so that all operations must be accomplished remotely, from the operational base at the surface. And the space available for coupling between the tubing hanger and the handling tool is relatively small, typically a cylindrical bore of a diameter on the order of 13 inches. Further, while the handling tool can be attached to the tubing hanger by direct manual operation on the operational base, before the hanger is run in and landed on its intended support in the wellhead or like structure, subsequent disconnection of the handling tool from the tubing hanger, after successfully landing the hanger, must be accomplished remotely, and it may thereafter be necessary to retrieve the tubing hanger and tubing strings, in which case re-connection of the handling tool to the hanger must be accomplished remotely. While much work has been done in this field in the past, there has been a continuing need for an improved remotely operated coupling.